Docs: Add 7.15.1 release

Author: spinscale

README.md

@@ -11,6 +11,7 @@ Note that Elasticsearch has native support for langdetection nowadays using the
 | ES    | Command |
 | ----- | ------- |
 | 8.0.0-alpha2 | `bin/elasticsearch-plugin install https://github.com/spinscale/elasticsearch-ingest-langdetect/releases/download/8.0.0-alpha2.1/ingest-langdetect-8.0.0-alpha2.1.zip` |
+| 7.15.1 | `bin/elasticsearch-plugin install https://github.com/spinscale/elasticsearch-ingest-langdetect/releases/download/7.15.1.1/ingest-langdetect-7.15.1.1.zip` |
 | 7.15.0 | `bin/elasticsearch-plugin install https://github.com/spinscale/elasticsearch-ingest-langdetect/releases/download/7.15.0.1/ingest-langdetect-7.15.0.1.zip` |
 | 7.14.2 | `bin/elasticsearch-plugin install https://github.com/spinscale/elasticsearch-ingest-langdetect/releases/download/7.14.2.1/ingest-langdetect-7.14.2.1.zip` |
 | 7.14.1 | `bin/elasticsearch-plugin install https://github.com/spinscale/elasticsearch-ingest-langdetect/releases/download/7.14.1.1/ingest-langdetect-7.14.1.1.zip` |